CEDAR: Verification of the Theory of Multiple Scattering of High-Frequency (HF) Signals in the Ionosphere with Small-scale Irregularities

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

The theory of multiple scattering of MF/HF radio waves by intermediate-scale (0.1-2 km) ionospheric irregularities predicts a very distinctive distribution of the integral intensity of a signal reflected from the ionosphere in the vicinity of a ground-based transmitter. In particular, it is significantly reduced within a distance of about several tens of kilometers orthogonal to the magnetic meridian. There then occurs a ring of enhancement at a greater distance. At still larger distances from the transmitter, effects of multiple scattering are weakened and the integral intensity returns to its undisturbed value. As represented in three dimensions, the shape of this dependence resembles an inverted "cowboy hat". While there are experimental confirmations of this "anomalous attenuation" effect near the transmitter location, no attempt has yet been made to track the intensity features at the larger distances important for the "Cowboy Hat" effect. An experiment of this kind is critical for confirmation of the theory, and it is the main objective of this project. Detection of the "Cowboy Hat" effect requires an ability to perform measurements at various points within 100-200 km distances from the transmitter in a matter of hours. An automobile-mounted installation will be used for this purpose, comprising a Radio Vector Field Sensor (an instrument developed by the Swedish Institute of Space Physics), a controlling laptop computer, and a standard GPS receiver. Any MF/HF radar providing pulse reflections from the ionosphere will serve the purposes of this project. Ionospheric reflections produced by the MF radar of the Platteville Atmospheric Observatory located near Platteville, Colorado and by the Boulder ionosonde will be explored. Each data acquisition session will be done during car journeys in the West-East or North-South directions, centered approximately at the radar's latitude or longitude and long enough to cross the Cowboy Hat's" walls. Twenty to thirty sessions should be sufficient to provide the necessary statistics. Broader impacts of the project include advances in understanding of processes in the upper atmosphere related to application of various remote sensing techniques. A graduate student will participate in the project. The broadcast and communications industries and their government regulators can directly use results of this project. The theory of multiple scattering has potential applications in fields important for the Aeronomic, Space-Weather and CEDAR communities: in diagnostics of intermediate-scale ionospheric irregularities, in interpretation of heating experiments, in MF/HF and satellite communications. There are implications of multiple scattering theory for plasma fusion diagnostics and for the physics of the solar corona.